1. Field of the Invention
The present invention relates to a cartridge which accommodates a recording medium in a case and is provided with a write-protect function which switches between a state in which recording to the recording medium is enabled and a state in which recording is disabled.
2. Description of the Related Art
Cartridges which accommodate recording media in cases are used as external recording media for computers and the like. Specifically, these cartridges may have a structure in which a recording medium is rotatably accommodated in a case which is formed to be hollow by matching peripheral walls of an upper case and a lower case together with one another. The recording medium may be a recording tape wound on a reel, or a disc-form disc medium.
Such a cartridge may be provided with a write-protect portion for preventing mistaken erasure of data that has been recorded to the recording medium. The write-protect portion may have a known structure which includes, for example, an operation hole, a through-hole and a switching member. The operation hole penetrates through a rear wall, which is at a side of the case which is opposite to a side thereof from which the case is loaded at a drive device. The through-hole is provided penetrating through a floor plate of the lower case. Consequent to operation of an operation member, which is exposed through the operation hole, from outside the case, the switching member moves along the floor plate and opens or closes the through-hole. When the through-hole is a long hole, the switching member opens or closes one end portion of this long hole.
That is, with the write-protect portion, a state in which recording to the recording medium by a drive device is disabled, for example, a state in which the switching member closes off the through-hole, can be attained and a state in which recording to the recording medium by a drive device is enabled, such as a state in which the switching member opens up the through-hole, can be attained. Thus, it is possible to switch (a recording permission) alternatively between this recording disabled state and recording enabled state. Switching of this recording permission for the recording medium is implemented by operating the operation portion from outside the case as described above and moving the switching portion to a recording disabled position (for example, a closed position) or a recording enabled position.
A relationship between this switching member (operation portion) and through-hole (case) will be described with reference to FIG. 12. As is shown in FIG. 12, an operation portion 104 is protrudingly provided at a switching member 102, which is disposed to be slidable against an inner face 100A of a rear wall 100 of the case. The operation portion 104 penetrates through the rear wall 100 and is exposed through a through-hole 106. A distal end portion of the operation portion 104 is set so as not to protrude beyond an outer face 100B of the rear wall 100, such that the operation portion 104 is not inadvertently caught on and the recording permission is not inadvertently switched.
Taper surfaces 106A and 106B, which are inclined such that an opening width of the through-hole 106 broadens at the outer face 100B side thereof, are formed at two edge portions of the through-hole 106 in a direction of movement of the switching member 102 (the direction of the arrow shown in FIG. 12). Accordingly, the operation portion 104 can be operated from gaps C which are formed between the operation portion 104, whose distal end does not protrude beyond the rear wall 100, and the taper surfaces 106A and 106B.
However, in a cartridge that is provided with a conventional write-protect portion as described above because the gaps C formed between the operation portion 104 and the taper surface 106A are small, the operation portion 104 must be operated with a small thing such as a user's fingernail or a pen tip. Accordingly, an improvement in operability when the recording judgment is to be switched has been called for.
As a measure therefor, setting through-hole 106 side end portions of the taper surface 106A and the like to the inner face 100A side and widening the gaps C has been considered. However, if a sufficient gap C is to be attained within a limited range of thickness of the case, distal ends at edge portions of the through-hole 106 become sharp, and sharp edges are formed. These sharp edges are a cause of formation failures, or a deterioration in strength when dropped. Accordingly, further measures have been called for.